gcf-proxy 0.6.0

Bidirectional MCP proxy that translates between JSON and GCF. 79% fewer input tokens, 63% fewer output tokens. Zero code changes.

gcf-proxy

Bidirectional MCP proxy that translates between GCF and JSON. Drop-in, zero code changes to your server or client.

79% fewer input tokens. 63% fewer output tokens. 90.7% comprehension accuracy across 10 models and 3 providers. 1,300+ LLM evaluations. Zero training.

Docs: gcformat.com · Proxy Guide · Playground · GCF vs TOON

Install

pip install gcf-proxy

Setup (one line change)

Before:

{"mcpServers": {"yours": {"command": "your-mcp-server"}}}

After:

{"mcpServers": {"yours": {"command": "gcf-proxy", "args": ["your-mcp-server"]}}}

Works with Claude Code, Claude Desktop, VS Code, Cursor, and any MCP client.

What it does

Translates in both directions:

Responses:  Your Server (JSON) -> gcf-proxy encodes -> LLM reads GCF   (79% input savings)
Requests:   LLM writes GCF    -> gcf-proxy decodes -> Your Server (JSON) (63% output savings)

• Responses: JSON tool results from the server are encoded as GCF
• Requests: GCF strings in tool call arguments are decoded to JSON (4-byte prefix check, zero overhead)
• Non-convertible content passes through unchanged in both directions
• Neither the server nor the client needs to know about GCF

Savings

JSON   2,506 bytes  ~626 tokens
GCF      916 bytes  ~229 tokens   (63% fewer)

With session dedup (92.7% by 5th call) and delta encoding (81.2%), use the GCF libraries directly.

Benchmarks

Format	Accuracy	Tokens	vs JSON
GCF	90.7% avg (10 models)	11,090	79% fewer
TOON	68.5% avg	16,378	69% fewer
JSON	53.6% avg	53,341	baseline

Also available on

• npm: npm install -g @blackwell-systems/gcf-proxy
• Go: go install github.com/blackwell-systems/gcf-proxy@latest

Links

• Full Setup Guide
• GCF Specification
• GCF vs TOON
• GitHub